Currently, mobile phone terminals and mobile networks using the third generation W-CDMA (Code Division Multiple Access) technology and the like use a circuit-switched (CS) system to implement voice telephony. Signals from mobile phones are received by a radio base station and then collected by an RNC (Radio Network Controller). A circuit-switched protocol is used to connect these signals to a circuit switching equipment on a mobile circuit-switched network, thereby implementing a voice telephony service.
The above mobile network uses a circuit-switched (CS) system to implement a voice telephony service. However, in response to a trend toward an IP-based mobile core network, there is a trend of configuring an IMS (IP Multimedia Subsystem) network and introducing a gateway apparatus (referred to as a second gateway apparatus in the detailed description) that interconnects a circuit switching equipment and the IMS network. In this case, a radio base station receives a signal from a mobile phone and an RNC collects the signal received by the radio base station. The RNC connects the signal using a circuit-switched protocol to the above gateway apparatus located at a boundary between a mobile circuit-switched network and the IMS network. Likewise, a terminal on the other side is connected to a gateway apparatus located at the boundary between a mobile circuit-switched network and an IMS network via an RNC. The gateway apparatuses are connected together on an IMS network to implement a voice telephony service.
With research and development of high-speed and large-capacity technology for mobile network, the future trend of mobile network is towards achieving higher speed and larger capacity based on the IP. At the present time,
HSDPA (High Speed Downlink Packet Access),
HSPA (High Speed Packet Access),
EVDO Rev. A, and
EVDO Rev. B
have already been put to practical use.
In the future, a further increase in speed is expected, and for example, LTE (Long Term Evolution) and EPC (Evolved Packet Core) are expected to be introduced. LTE aims at 100 and 50 Mbps (megabits per second) or higher in downlink and uplink directions, respectively, and EPC is an IP backbone network supporting LTE.
It is necessary to support voice communication continuously also for terminals which are going to be connected to such LTE and EPC expected to appear in the future.
Whether terminals connected to LTE and EPC need to support a conventional circuit-switched voice communication function or VoIP (Voice over IP) voice communication function is still under debate in the 3GPP (3rd Generation Partnership Project). While no determination has been made yet (at the time of filing of the present application), no matter which functions will be supported, interconnection with existing circuit-switched voice communication needs to be ensured.
Regarding a gateway, for example, Patent Document 1 discloses a gateway for connecting networks of different types. This gateway connects a first network and a second network that uses a signal format different from that of the first network. The gateway comprises: a conversion unit that converts a signal used in the first network into a signal used in the second network and converts a signal used in the second network into a signal used in the first network, when communication is performed between a terminal connected to the first network and a terminal connected to the second network; a detection unit that detects conversion process information including at least one of a conversion time required by the conversion unit to convert the signal and the amount of data converted; and a network connection unit that is connected to at least one of the first and second networks and transmits the conversion process information to a charging system of the first or second network. The conversion unit converts at least one of a call process signal generated by call connection signaling, a voice signal generated by an audio codec, and a video signal generated by a video codec. In the above Patent Document 1, a gateway between an Internet service provider (ISP) network and a 3G network creates information for executing volume charging. Patent Document 1 does not disclose a gateway that causes a packet transfer apparatus provided on a mobile high-speed network to operate like an RNC and connects the packet transfer apparatus to a circuit switching equipment provided on a mobile circuit-switched network, to implement interconnection of voice communication between a terminal connected to a mobile high-speed network and an existing terminal connected to a circuit switching equipment via an RNC.
In addition, Patent Document 2 discloses a multimedia information relay apparatus in which a conversion control means holds an attribute conversion table indicating conversion process contents, if multimedia information entered from a first multimedia communication terminal can be supplied to a second multimedia communication terminal, only through a conversion processing (conversion of attributes such as a coding scheme; a coding rate, and a multiplexing parameter, and the like). A video and audio conversion means of the multimedia information relay apparatus converts video and audio information, respectively, included in the multimedia information entered from the first multimedia communication terminal, in accordance with the contents of conversion processing indicated in the attribute conversion table. After the conversion, the video and audio conversion means supplies the converted information to the second multimedia communication terminal. The relay apparatus disclosed in the above Patent Document 2 converts a coding rate and the like, in accordance with capabilities (video/audio coding and decoding capabilities, for example) between the first and second multimedia communication terminals. However, Patent Document 2 does not disclose a gateway that causes a packet transfer apparatus provided on a mobile high-speed network to operate like an RNC and connects the packet transfer apparatus to a circuit switching equipment on a mobile circuit-switched network, to interconnect voice communication between a terminal connected to the mobile high-speed network and an existing terminal connected to the circuit switching equipment via an RNC.
Patent Document 3 discloses a configuration in which a mobile terminal on a home network is connected to an Internet service provider via an access point and a router. In addition, Patent Document 4 discloses a configuration in which a step that executes dynamic filtering of a data packet at an access gateway in a network, selects a security policy indicated by information inherent to the access gateway. These Patent Documents 3 and 4 do not disclose a gateway that causes a packet transfer apparatus provided on a mobile high-speed network to operate like an RNC and connects the packet transfer apparatus to a circuit switching equipment on a mobile circuit-switched network, to interconnect voice communication between a terminal connected to the mobile high-speed network and an existing terminal connected to the circuit switching equipment via an RNC.
Patent Document 5 discloses a configuration for communication between a fixed terminal on an IPv4 private network and an IPv6 global network interconnected thereto through a relevant IPv4 Internet. According to this configuration, the IPv4 private network (IPv4), the global IPv4 Internet (IN), and the IPv6 network (GV6) are interconnected through a first gateway (AGW) and a second gateway (BGW). In order to allow communication from a first fixed terminal (A1) on the IPv4 private network (PV4) to a second fixed terminal (B) on the IPv6 network (GV6), “IPv6 in IPv4 tunnels” (TUN′ and TUN″) are set up through the IPv4 private network (PV4) and the global IPv4 Internet (IN). Based on a global IPv6 address assigned to the first dual-stack terminal (A1), mapping tables can be set up in the first gateway (AGW) and the second gateway (BGW). The mapping tables are used for communication between the first terminal (A1) and the second terminal (B). The tunnels (TUN′, TUN″) are used in particular to avoid use of a Virtual Private Network (VPN) for communication initiated, from the first terminal (A1) to the second terminal (B). Patent Document 5 does not disclose a configuration of the present invention which will be described below.
Patent Document 1:
Japanese Patent Kokai Publication No. JP-P2004-222009A
Patent Document 2:
Japanese Patent Kokai Publication No. JP-P2005-072973A
Patent Document 3:
Japanese Patent Kokai Publication No. JP-P2008-210397A
Patent Document 4:
Japanese Patent Kohyo Publication No. JP-P2008-512958A
Patent Document 5:
Japanese Patent Kohyo Publication No. JP-P2007-524257A